Mechanisms of directional sensitivity in the visual system will be analysed by a combination of physiological, pharmacological and developmental techniques. Directionally sensitive cells in the rabbit retina will be recorded while various synaptic transmitters and their antagonists are applied, on the hypothesis that different synaptic transmitters will affect different aspects of the receptive field of these cells, or directionally sensitive cells differently from other types of cell. Cats will be raised in rotating striped drums to work out the period of greatest susceptibility for this kind of deprivation, and whether this critical period is the same as the critical period for monocular deprivation. The receptive fields of directionally sensitive cells in necturus retina and tectum will be analysed in detail, as a prelude to intracellular experiments in which the connections that form these receptive fields can be worked out.